I have always gotten good starting gravity, at least close or above what the recipe generator says it should be. But I hear all this talk about mash effeciency. What is it and how do I calculate how effecient I am mashing? Many thanks in advance.

I am not sure how the "max predicted gravity" is determined. According to the book, maltsters have maximum rates for what their different malts contribute to the SG. Someone else probably knows the answer to this part of the problem... Wait! I think I spot a first string brewmaster down field, hopefully he can catch this pass...

Have you tried figuring it using the Finished Beer Analysis? This tool was designed precisely with this task in mind. Enter your ingredients and amounts, your original and terminal gravities and temperatures for each, and calculate the result. You will receive results containing your mash efficiency as well as your apparent attenuation